function newWindow(url, ancho, alto, target) {
	posX = (parseInt(screen.availWidth)-ancho)/2;
	posY = (parseInt(screen.availHeight)-alto)/2;
	window.open(url, target, "scrollbars=no,status=no,toolbar=no,location=no,directories=no,menubar=no,width="+ancho+",height="+alto+",left="+posX+",top="+posY+",resizable=0,scroll=yes");
}